Alignment of information systems (IS) strategy with business strategy is a top concern of both the chief information officer (CIO) and the top management team (TMT) of organizations. Even though researchers and key decision makers in organizations recognize the importance of IS strategic alignment, they often struggle to understand how this alignment is created. In this paper, we develop a nomological network in which shared understanding between the CIO and TMT about the role of IS in the organization (which represents the social dimension of IS strategic alignment) is posited to be a proximal antecedent of the intellectual dimension of IS strategic alignment. We further posit that shared language, shared domain knowledge manifest in the CIO’s business knowledge and the TMT’s strategic IS knowledge, systems of knowing (structural and social), and CIO- TMT experiential similarity are important determinants of this shared understanding. Data were collected from 243 matched CIO-TMT pairs. Results largely support the proposed nomological network. Specifically, shared understanding between the CIO and TMT is a significant antecedent of IS strategic alignment. Furthermore, shared language, shared domain knowledge, and structural systems of knowing influence the development of shared understanding between the CIO and the TMT. Contrary to expectations and to findings of prior research, social systems of knowing, representing informal social interactions between the CIO and TMT, and experiential similarity did not have a significant effect on shared understanding.